The Fairy Godmother could make an appearance as a wise advisor to Mal. She could offer advice on matters of magic and governance. Carlos could also be a great support, using his knowledge of technology (even if it's a bit more modern - ish in the context of the isles) to improve the infrastructure or create new defenses for the kingdom.
One idea could be Mal having to face a new, powerful villain from a forgotten part of the isles. This villain could be threatening to take over all the territories Mal has united. Another could be Mal going on a journey to discover more about her family's past and unearthing secrets that change her perception of herself and her role as queen.
Isles would be an obvious great supporting character. She could offer medical advice to Jane during her pregnancy, as well as be there for her emotionally. Maura's scientific mind could also come in handy when it comes to things like baby - related research or understanding the pregnancy process better.
Evie could be a great supporting character. She might come over to help Mal decorate the new place with her amazing fashion sense. Jay could also be there, helping Ben move in the heavy furniture. And maybe Dizzy could pop in from time to time to add some fun and chaos with her unique charm.
Evie could be one of her allies. They are friends, and Evie is smart and can offer good advice on how to rule. Also, Jay might be on her side. He's strong and brave, which would be useful for protecting Mal as she tries to become queen.
Finn would be a great supporting character. He has been Rey's friend from the start and his loyalty and combat skills could be very useful. Poe Dameron is another one. His piloting abilities and leadership could assist Rey in her adventures. Also, BB - 8 could be there, providing comic relief as well as being a useful droid for various tasks like hacking or providing information.
For the Pirate Isles side, a swashbuckling pirate captain like Captain Blackbeard could be a main character. He could bring his tough and adventurous spirit into the Mystreet world. On the Mystreet side, Aaron could be a main character. His strength and loyalty would be interesting to see when dealing with the pirates.
Maleficent is often a significant supporting character. Since Mal is her daughter, her presence can add a lot of drama. Another could be the three good fairies from Aurora's story. They might be there to give Aurora advice or protect her. Prince Phillip could also show up, especially if the story involves a love triangle or some sort of relationship dynamic between Aurora, Mal, and him.
Well, it could be about Mal facing various challenges in the isle and proving herself worthy of being the queen. Maybe she has to outwit her rivals, solve problems in the isle like dealing with power - hungry villains or uniting the different factions there.
One great supporting character could be Velvet. As a Faunus like Blake, she could understand Blake's experiences on a deeper level. They could bond over their shared heritage and Velvet could provide Blake with different perspectives on how to deal with Faunus - related issues. Another option is Qrow. His experience and knowledge of the world of Remnant could be invaluable to Blake. He could act as a mentor figure, guiding her through difficult situations. And finally, Penny. Her unique nature and innocent view of the world could offer a fresh take on things for Blake, and her combat abilities could also come in handy in dangerous situations.
Her best friend from school could be a great supporting character. They could provide a normal perspective and also be someone Spider Girl can confide in. Another could be an older superhero who acts as a mentor to her, guiding her through the challenges of being a superhero.